Thermal marking system

ABSTRACT

One or more arrays of heating elements are configured with insulating regions to prevent the dissipation of heat to unintended regions of a thermochromic substrate. Methods include printing and arranging impressions on a two-sided substrate avoiding bleeding and other problems more-commonly associated with traditional two-sided thermal printing techniques. A simple and reliable thermal printing system is provided for use in ballot marking, including several mechanisms for receiving and detecting the orientation of a substrate within a thermal printing apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional of co-pending U.S. patentapplication Ser. No. 13/288,871, filed Nov. 3, 2011, which is adivisional of U.S. patent application Ser. No. 12/340,361, filed Dec.19, 2008, now U.S. Pat. No. 8,085,285, issued Dec. 27, 2011 and whichclaims priority from U.S. provisional patent application No. 61/015,158,filed Dec. 19, 2007, each of which are hereby incorporated in theirentirety by this reference thereto.

BACKGROUND OF THE INVENTION

1. Technical Field

The invention relates to the field of thermal printing. Morespecifically, the invention relates to thermal printing techniques forproducing markings on multiple sides of a thermochromic medium.Particular embodiments of the invention are particularly useful inthermal printing applications to mark votes on a two-sided ballot duringan election to provide visual evidence of voters' selections.

2. Description of the Related Art

In general, thermal printing methods produce an image by selectivelyheating a thermochromic medium using a thermal printer head. Thermalprinting is typically practiced by first applying a coating ofthermochromic dye to a substrate, resulting in a thermochromic medium.Thermochromic dye is responsive to heat and changes its appearance whenheat-activated, resulting in a marking. After an application of dye, theprocess continues by selectively applying heat to various regions of thethermochromic medium, thus leaving markings on the medium.

However, various problems exist in the field of thermal printing. Forexample, as heat naturally dissipates, bleeding may occur, thus markingunintended regions of the medium. In particular, a marking on one sideof the printing medium may conduct through the substrate, resulting inan unintended marking on the opposite side.

Recent controversies surrounding the accuracy of electoral systems haveled to the development of direct recording electronic (DRE) votingmachines that, according to proponents, minimize the number ofinadvertently spoilt ballots. Critics of DRE machines, however,challenge the resulting lack of a voter verifiable paper trail.Consequently, hybrid systems have been proposed in which an electronicvoting machine, e.g. a computer with a touch sensitive display, assistsvoters in marking a paper ballot that may be inspected by the voterprior to optical scanning. In these systems the ballots are archivedshould the counting procedure be subsequently contested.

Thermal printing is an attractive technology for use in ballot markingsystems on account of the simple and reliable printing mechanism and therelatively low resolution of typical ballot markings. However, asexplained above, an unintended marking of a ballot due to theshortcomings of the current state of the art negates the advantages ofemploying a thermal printing system to record votes.

Furthermore, the majority of existing thermal printing systems arecapable of printing only on a single side of each sheet of thermochromicmedia. Typically, a thermochromic coating is applied to only one side ofthe substrate. However, when marking printable media, a desire forreadability and simplicity strongly motivates printing on both sides ofa single sheet of thermochromic media. In the case of a ballot, limitinga printable media to a single sheet simplifies ballot handling andimproves the integrity of the election by eliminating the possibility ofa split ballot. Yet the length of many ballots, especially those withmultiple voter initiatives, makes compressing all election issues onto asingle side of a single sheet a difficult endeavor if readability is tonot be compromised. The increased surface area available to two-sidedprinting systems strongly motivates the use of a printing system withtwo-side printing capability.

Various two sided thermal printing systems have been proposed, buttypically either increase the complexity of the heating element controlsystem or require a substrate of sufficient thickness and insulatingcapability as to prevent heat conduction from one side to the other.However, simpler approaches would be highly desirable for use in ballotmarking.

Of course, any thermal printing system must ensure uniform thermalcontact between the thermochromic ballot and the heating elements thatproduce the markings. Indeed, ensuring proper contact in the case ofmarking ballots presents special challenges. This is because the ballotsare necessarily handled by voters themselves, who may or may not befamiliar with thermal printing technology. Thus, there is a need for asimple yet reliable mechanism for ensuring uniform contact between theballot and the heating elements after the ballot is received from thevoter.

SUMMARY OF THE INVENTION

In some embodiments of the invention, a fixed size and layout of aprintable medium allows the use of a fixed array of heating elementsthat remain stationary relative to the printing medium during printing,greatly simplifying the printing procedure.

In some embodiments of the invention, a system and apparatus aredisclosed comprising one or more arrays of heating elements configuredwith alternating heating regions and insulating regions to selectivelyheat regions on a substrate treated with a thermochromic coating.

In some embodiments, two or more arrays of heating elements are disposedfacing towards each other and are configured with a slot to accept atwo-sided medium formed with thermochromic coatings on each side of asubstrate. According to these embodiments, techniques are disclosed forprinting on a two-sided medium, as well as techniques for designing atwo-sided medium to mitigate the adverse effects typically associatedwith the conduction of heat away from the applied location and throughthe substrate, as well as other problems more-commonly associated withtraditional two-sided thermal printing techniques.

In some embodiments, the two-sided medium is a voting ballot. Similarly,some embodiments of the invention provide simple and reliable thermalprinting systems for use in ballot marking. The ballot markings areproduced by a heating element array (HEA) in thermal contact with theballot.

The invention also provides an apparatus for receiving and orienting athermochromic medium. Likewise, methods of receiving and orientating avoting ballot are also disclosed that, while simple for the voter tooperate, ensure reliable thermal contact between the ballot and the HEA.In particular, the receiving and orienting mechanisms are capable ofaccepting either folded or unfolded ballots in any orientation, greatlyreducing the opportunities for voter error. In some embodiments,orientation indicators and/or sensors are employed to automatically tella processor about the orientation of a ballot inserted into the votingmachine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic side view of a heating element array (HEA) formarking a thermochromic medium according to some embodiments of theinvention;

FIG. 1B is a schematic isometric view of a single plate of a heatingelement array according to some embodiments of the invention;

FIG. 2A is a visual representation of a ballot taking advantage of atechnique for thermally marking a ballot on both sides according to someembodiments of the invention;

FIG. 2B illustrates the steps of a method of designing a two-sidedthermochromic medium according to some embodiments of the invention;

FIG. 2C illustrates the steps for a method of designing a two-sidedthermochromic medium and thermally printing marks on checkboxesaccording to some embodiments of the invention;

FIG. 3A illustrates the steps for a method of designing a two-sidedthermochromic medium according to some embodiments of the invention;

FIG. 3B illustrates the steps for a method of designing a two-sidedthermochromic medium and thermally printing marks on checkboxesaccording to some embodiments of the invention;

FIG. 3C is a visual representation of a ballot taking advantage of analternative technique for thermally marking a ballot on both sidesaccording to some embodiments of the invention;

FIG. 4A shows several configurations ensuring reliable contact between asubstrate and a heating element array according to various embodimentsof the invention;

FIG. 4B is an isometric view of two printed circuit boards havingheating elements disposed on one side of each board according to someembodiments of the invention;

FIG. 4C shows front and rear views of a thermochromic medium used withthe heating element apparatus shown in FIGS. 4B and 4D;

FIG. 4D is a side view of two printed circuit boards having heatingelements disposed on one side of each board with a thermochromic mediumdisposed therebetween according to some embodiments of the invention;

FIG. 5 is an isometric view of a voting machine according to someembodiments of the invention;

FIG. 6 illustrates a ballot labeling scheme and associated sensorpositions for orienting a ballot according to some embodiments of theinvention; and

FIG. 7 illustrates four possible ballot orientations capable of beingidentified by a thermal printing machine according to some embodimentsof the invention.

DETAILED DESCRIPTION OF THE INVENTION

Some embodiments of the invention comprise an apparatus with one or morearrays of heating elements configured with heating regions andinsulating regions to selectively heat selected areas of a substratetreated with a thermochromic coating.

Heating Element Arrays

FIG. 1A shows a heating element array (HEA) for marking a thermochromicmedium according to the invention. In the presently preferred embodimentof the invention, the thermochromic medium is a ballot 500. However, itwill be readily apparent to those having ordinary skill in the arthaving the benefit of this disclosure that the invention may be used tomark a wide array of thermochromic media to yield a correspondingly widearray of printed materials.

The ballot 500 is positioned between the HEA 100 and an insulator 200.In this and the following figures, the ballot 500, HEA, and insulator200 are shown with a small separation for clarity. In actual use, thesecomponents are preferably in direct thermal contact with one another.

According to presently preferred embodiments of the invention, theheating elements 121 and 122 within the HEA are surrounded by aninsulating substrate 110. The heating elements can be heatedindividually to mark the ballot 500 as desired. The insulating substrate110 and insulator 200 help contain the applied heat to the immediatevicinity of the heating element such that the mark produced by anindividual heating element 121 or 122 is limited to the dimensions ofthe heating element 121 or 122, respectively. As such, it is easy todesign a ballot or other thermochromically printed materials.

In some embodiments of the invention, the HEA is constructed using aprinted circuit board (PCB). The heating elements may be either surfacemount resistors or shaped traces. While shaped traces allow for moreprecise control of the shape of the marking produced on the ballot,surface mount resistors provide sufficient resolution for manyapplications. Notably, the commonly available “0201” surface mountpackage is capable of producing a marking as small as 0.002 in by 0.001in.

Since the ballot 500 can only be marked when positioned near the heatingelement 121, and 122, the heating elements 121, and 122 are preferablyarrayed in a regular pattern and substantially cover the entire extentof the ballot 500. FIG. 1B is an isometric view of a plate incorporatinga heating element array 130 containing a matrix of heating elements,indicated by filled boxes, separated by rows and columns of insulatingsubstrate, indicated by empty boxes. Using a matrix of heating elements,like the matrix illustrated in FIG. 1B, allows the HEA to be used formany different printing layouts, and greatly simplifies the ballotdesign processes.

A heating element array using a matrix pattern of heating elements isparticularly useful in printing applications in which the medium to beprinted upon comprises a plurality of check boxes or the like. Accordingto some embodiments of the invention, a method of designing a check boxmedium is provided to specifically match the design of the heatingelement array. Check box type applications typically associate the checkboxes with some other text. For example, a voting ballot typicallyincludes a list of candidates written in text with an associatedcheckbox logically placed proximate to the text to indicate one's votefor that candidate. The invention provides solutions for designing acheck box medium to be used for ballot markings in two-sided thermalprinting environment.

In the presently preferred embodiment of the invention, a ballot isdesigned for a thermal printing system such that voting choices arememorialized. According to some embodiments, a ballot is designed for athermal printing voting machine, wherein the ballot and printer areconfigured such that the machine accurately marks the ballotirrespective of the orientation of the ballot within the machine. Toaccomplish this aspect of the invention, one or more ballot orientationindicators and one or more corresponding sensors are utilized asexplained below.

Two-Sided Thermal Printing

The invention provides techniques for manufacturing a thermochromicmedium by treating a substrate with a thermochromic coating on bothsides and applying heat to on one side of the medium such that the heatwill not produce a visible marking on the other side of the medium. Themanufacturing techniques provide this functionality despite assumingthat heat applied to one side of the medium will conduct through thesubstrate with a sufficient intensity to activate a thermochromiccoating applied to the opposite side of the substrate.

FIG. 2A shows a visual representation of a technique for thermallymarking a ballot on both sides according to the invention. In thisexample, the thermochromic medium is described as a ballot 500 based ona paper substrate. However, it will be readily apparent to thosepossessing ordinary skill in the art that any thermochromic medium maybenefit from the technique.

In this technique, a thermochromic coating is applied to selectedregions on each side of the substrate in an exclusionary fashion.According to these techniques, no region of paper exists in whichthermally sensitive coatings are applied to both sides of the paper. Onthe front of the ballot 500, the sets of candidates running for severaloffices are press printed at left. The boxes 531 for indicating avoter's preference for a particular candidate are press printed in avertical column at right. The entire column of boxes is backed by athermochromic coating 521. On the back of the ballot, a series ofservices are press printed below a set of press printed instructions,and a set of boxes 532 for indicating the voter's perceived importanceof each service is press printed below each service. The sets of boxes,and portions of the printed services, are backed by a thermochromiccoating. The thermochromic coatings applied to each side are offset fromone another. That is, the region 522 opposing the coated region 521 onthe front of the ballot is free of thermochromic coating, and the region524 opposing the coated region 523 on the back of the ballot is free ofthermochromic coating. This exclusionary approach to applying thethermochromic coating ensures that when marks are created on one side ofthe ballot, no unintended marks are produced on the opposing side of theballot.

FIG. 2B illustrates the steps of a method 201 of designing a two-sidedthermochromic medium according to some embodiments of the invention. Insome embodiments of the invention, the two-sided thermochromic medium isa voting ballot. However, it will be readily apparent to those havingordinary skill in the art having the benefit of this disclosure, thatthe method of designing a two-sided thermochromic medium is useful in avariety of other applications.

The method begins with providing a two-sided substrate at step 202. Themethod 201 continues by establishing various queries and checkboxes atstep 203, wherein the checkboxes accept one or more indicia representinga response to the various queries. In some embodiments of the invention,two sets of queries and corresponding checkboxes are established,wherein the one set is positioned on the front of the two-sidedthermochromic medium and the second set is positioned on the back of thetwo-sided printing medium. In the presently preferred embodiment thefirst checkbox region does not line up through the two-sided printingmedium to a thermochromic coating in a second checkbox region. Rather,the queries and checkboxes are designed and established in anexclusionary manner such that an application of thermochromic coating ina first checkbox region does not line up through the two-sided printingmedium to a second checkbox region.

It will be readily apparent to those having ordinary skill in the arthaving the benefit of this disclosure that a wide variety and number ofsets of queries and corresponding checkboxes are able to be positionedin a similar exclusionary manner on a wide variety of positions on themedium.

At step 204 the method 201 continues with printing the two-sidedsubstrate with the established queries and checkboxes. In the presentlypreferred embodiment of the invention, the queries and checkboxes arepress printed. However, it will be readily apparent to those havingordinary skill in the art having the benefit of this disclosure that avariety of printing methods, now known or later developed, may be usedto print the queries and checkboxes.

The method of designing a two-sided thermochromic medium 201 continueswith treating the region of the substrate backing the checkboxes with athermochromic coating at step 205.

FIG. 2C illustrates a similar method 201′ of designing a two-sidedthermochromic medium and thermally printing marks on checkboxesaccording to some embodiments of the invention. According to FIG. 2C,steps 202, 203, 204, and 205 are repeated from the method 201 of FIG.2B. Additionally, the method continues with placing the treated printingmedium in thermal contact with an array of heating elements at step 206and applying heat to various checkboxes at step 207, thus printingmarks.

In some other embodiments of the invention, the methods 201 and 201′further comprise providing at least one orientation indicator on thethermal printing medium. As explained below, orientation indicators areemployed to detect the orientation of a thermal printing medium suchthat the thermal printing medium is marked accurately irrespective ofits orientation relative to the HEA. According to these embodiments, thethermal printing system is more user-friendly.

FIGS. 2B and 2C illustrate one way to designing a printable medium suchthat markings are not visible through the printable medium. FIGS. 3A and3B illustrate another method of printing unintended marking through theuse of masking. Similarly, 3C illustrates a printable medium takingadvantage of these masking methods.

FIG. 3A illustrates the steps of a method 301 of designing a two-sidedthermochromic medium using a substantially opaque masking according tosome embodiments of the invention. In some embodiments of the invention,the two-sided thermal printing medium is a voting ballot. However, itwill be readily apparent to those having ordinary skill in the arthaving the benefit of this disclosure, that the method of designing atwo-sided thermochromic medium is useful in a variety of otherapplications.

The method begins with providing a two-sided substrate at step 302. Themethod 301 continues by establishing various queries and checkboxes atstep 303, wherein the checkboxes accept one or more indicationsrepresenting a response to the various queries. Two sets of queries andcorresponding checkboxes are established, wherein the one set ispositioned on the front of the two-sided printing medium and the secondset is positioned on the back of the two-sided printing medium.

At step 304 the method 301 continues with printing the two-sidedsubstrate with the established queries and checkboxes. In the presentlypreferred embodiment of the invention, the queries and checkboxes arepress printed. However, it will be readily apparent to those havingordinary skill in the art having the benefit of this disclosure that avariety of printing methods, now known or later developed, may be usedto print the queries and checkboxes. The step 304 of printing one ormore checkboxes results in creating one or more “shadow areas” on theopposite side of the printable medium. The shadow areas comprise thearea on the opposite side of the printable medium that is vulnerable toan unintended mark caused by heating the opposing checkbox area.

The method 301 continues with the step 305 of masking the first sideshadow area and the second side shadow area with a substantially opaquecoating. As used herein, the term “opaque” refers to a condition of aregion on the printable medium in which a mark caused by the heating athermochromic coating in that region is unnoticeable. In someembodiments, the opaque coating comprises dark ink. The benefit of thismasking technique is that a user can simply treat the entirety of bothsides with the thermochromic coating, resulting in an easier and lessexpensive coating process. Furthermore, the masking ensures that themarks coming through to an unintended side of the printing medium arenot visible.

The method of designing a two-sided thermochromic medium 301 continueswith treating the substrate with a thermochromic coating at step 306. Insome embodiments of the invention, at least the checkboxes are treatedwith the thermochromic coating. In some other embodiments of theinvention the entire substrate is treated with the thermochromic coatingthereby resulting in an easier treatment process.

FIG. 3B illustrates a method 301′ of designing a two-sided thermochromicmedium and thermally printing marks on checkboxes according to someembodiments of the invention. According to FIG. 3B, steps 302, 303, 304,305, and 306 are repeated from the method 301 of FIG. 3A. Additionally,the method continues with placing the treated printing medium in thermalcontact with an array of heating elements at step 307 and applying heatto various checkboxes at step 308, thus printing marks.

In some other embodiments of the invention, the methods 301 and 301′further comprise providing at least one orientation indicator on thethermal printing medium. As explained below, orientation indicators maybe employed to detect the orientation of a thermal printing medium suchthat the thermal printing medium may be marked accurately irrespectiveof its orientation within the HEA. According to these embodiments, thethermal printing system is more user-friendly.

FIG. 3C shows a ballot resulting from the masking technique forthermally marking a printable medium on both sides according to theinvention. Again, although the thermochromic medium is described as aballot, it will be readily apparent to those possessing ordinary skillin the art that any thermochromic medium may benefit from the technique.In any region where thermal marking may occur on one side, an opaque inkis applied to the opposing side's shadow area to ensure that anyunintentional thermal markings on the opposing side are masked. On boththe front and back of the ballot shown in FIG. 3C, the sets ofcandidates running for several offices are press printed at left, andvoter preferences are thermally marked in a column of boxes at right.Because marks within these boxes may produce a marking on the opposingside of the ballot, dark-colored opaque vertical bars 561 and 562 arepress printed in the shadow area.

In the above approaches, the ability to thermally mark both sides of thethermochromic substrate allows the ballot designer to utilize theincreased surface area offered by both sides of the ballot. Theinvention presupposes that heat will in fact conduct through the paperand the invention prevents unintentional marking on the opposing side bythe masking. Thus, according to some embodiments of the invention, thepaper can be marked on both sides using heating elements on only oneside of the paper. This significantly speeds and simplifies the printingprocess in that the paper need not be flipped, either automatically orby the voter, before printing on the second side.

Ballot and Heating Element Array Positioning Techniques

FIG. 4A shows several heating element array (HEA) configurationsensuring reliable contact between a thermochromic medium and the HEAaccording to some embodiments of the invention. In the followingexamples, the thermochromic medium is described as a ballot, however, itwill be readily apparent to those possessing ordinary skill in the artthat any thermochromic medium may benefit from the technique.

1. HEA-Insulator Clamshell around Ballot

In some embodiments of the invention, a ballot 403 is clamped between anHEA 404 and an insulator 405 connected by a hinge 406. The insulator 405ensures firm, uniform contact between the ballot 403 and the HEA 404 andminimizes the transfer of heat away from the marked regions, therebyreducing any bleeding of the marks produced. If the ballot 403 is formedof sufficiently insulative paper, this configuration allows forfull-coverage marking on one side of the ballot 403. If more conductivepaper is used, this configuration allows for full-coverage, identicalmarking or exclusionary, distinct marking on opposing sides of theballot 403, as described above.

2. HEA Clamshell around Ballot

In some embodiments of the invention, a ballot 407 is clamped betweentwo HEAs 408, 409 connected by a hinge 410. An insulating substrate 412,413 is disposed between the heating elements 414, 415 within the HEAs408, 409. The insulating substrate minimizes conduction of heat awayfrom the marked regions of the ballot 407. If the ballot 407 is formedof sufficiently insulative paper, this configuration allows forfull-coverage, distinct marking on both sides of the ballot 407. If moreconductive paper is used, this configuration allows for full-coverage,identical marking or exclusionary, distinct marking on opposing sides ofthe ballot 407.

3. HEA Clamshell around Ballot Folded around Insulator

In some embodiments of the invention, a ballot 416 is folded around aninsulator 417. The folded ballot 416 is clamped between two HEAs 418 and419 connected by a hinge 420. Heating elements 422, 423 within the HEAs418, 419 thus mark onto the exterior side of the folded ballot 416. Theinsulator 417 prevents marking of one half of the folded ballot by theHEAs 422, 423 adjacent to the complementary half of the folded ballot416. The insulating substrate 417 between the heating elements 422, 423within the HEAs 418, 419 minimizes conduction of heat away from themarked regions. If the ballot 416 is formed of sufficiently insulativepaper, this configuration allows for full-coverage marking on theexterior side of the folded ballot 416. If more conductive paper isused, this configuration allows for full-coverage, identical marking orexclusionary, distinct marking on both exterior and interior sides ofthe ballot 416. In allowing for a folded ballot 416, this configurationreduces the effective size of the ballot 416, thus easing voter handlingof the ballot 416 without reducing the markable area. Furthermore, ifonly the exterior side of the folded ballot 416 is marked, voter privacycan be enhanced by inverting the folded ballot 416 upon removal from theballot marking device.

4. Insulator Clamshell around Ballot Folded around Two-Sided HEA

In some embodiments of the invention, a ballot 424 is folded around atwo-sided HEA 425. The two-sided HEA 425 may be constructed from asingle insulating substrate, e.g. a PCB, with heating elements 426, 427on either side, or from two single-sided HEAs abutted against oneanother with heating elements facing outward toward the interior side ofthe folded ballot 424. The two-sided HEA thus marks onto the interiorside of the folded ballot 424. The folded ballot 424 is preferablyclamped between two insulators 428, 429 that are connected by a hinge430. The insulators 428 and 429 ensure firm, uniform contact between thefolded ballot 424 and the heating elements 426, 427 within the two-sidedHEA 425 and minimize conduction of heat away from the marked regions. Ifthe ballot 424 is formed of sufficiently insulative paper, thisconfiguration allows for full-coverage marking on the interior side ofthe folded ballot 424. If more conductive paper is used, thisconfiguration allows for full-coverage, identical marking orexclusionary, distinct marking on both interior and exterior sides ofthe folded ballot 424. In allowing for a folded ballot 424, thisconfiguration reduces the effective size of the ballot 424, thus easingvoter handling of the ballot 424 without reducing the markable area.Furthermore, if only the interior side of the folded ballot 424 ismarked, voter privacy is enhanced.

5. HEA Clamshell around Ballot Folded around Two-Sided HEA

In some embodiments of the invention, a ballot is folded around atwo-sided HEA 432. The two-sided HEA 432 may be constructed from asingle insulating substrate, e.g. a PCB, with heating elements 433, 434on either side, or two single-sided HEAs abutted against one anotherwith heating elements 433, 434 facing outward toward the interior sideof the folded ballot 431. The insulating substrates 435 and 436positioned between the heating elements 433 and 434 of the HEA 432minimize conduction of heat away from the marked regions. If the ballot431 is formed of sufficiently insulative paper, this configurationallows for full-coverage marking on both the interior and exterior sidesof the folded ballot 431. If more conductive paper is used, thisconfiguration allows for full-coverage, identical marking orexclusionary, distinct marking on both interior and exterior sides ofthe folded ballot 431. In allowing for a folded ballot 431, thisconfiguration reduces the effective size of the ballot 431, thus easingvoter handling of the ballot 431 without reducing the markable area.Furthermore, if only the interior side of the folded ballot 431 ismarked, voter privacy is enhanced.

It will be readily apparent to those having ordinary skill in the artand having the benefit of this disclosure, that the examples given abovein (1)-(5) are merely some possible configurations. It will be obviousto ordinary practitioners that other configurations of heating elementarrays are envisioned to accomplish a wide variety of design specificgoals that may present themselves. For example, FIG. 4B is an isometricview of two PCBs 401 and 402 with heating elements 411, 421, 412, and422 disposed on one side of each board. The two PCBs 401 and 402illustrated in FIG. 4B are disposed facing each other, such that athermochromic medium 499 inserted between the PCBs is exposed to heatingelements on each side. In some embodiments the heating elements are“nested” within the substrate or insulator. Furthermore, the two PCBs401 and 402 have alternating rows of heating elements such that any oneregion on the medium placed between the PCBs is only heated by one ofthe PCBs 401 or 402.

As shown in FIG. 4C, the thermochromic medium 499 has checkboxes in rowson both the front and rear side disposed in an alternating fashion. Inthe presently preferred embodiment of the invention, the check boxes areindividually treated with a thermochromic coating such that the checkboxes are marked with the application of heat from a heating element.According to these embodiments, the invention utilizes the alternatingrows of heating elements and the alternating rows of coated checkboxesto cause heat by one or more heating elements to make a marking withoutinadvertently marking a checkbox on the opposing side of the ballot.

Receiving Ballot and Determining Ballot Orientation

The invention further provides mechanisms for receiving an unmarkedballot from the voter and determining the orientation of the receivedballot. FIG. 5 shows a voting machine 560 according to some embodimentsof the invention. In the presently preferred embodiment of theinvention, the voting machine 560 includes a pair of opposing PCBs 564and 565 with heating element arrays 566. The PCBs also includes paperorientation sensors 563, e.g. surface mount LED and receiver pairs, ateach corner. In some embodiments, the PCBs are mechanically coupled to apressing mechanism 561 and rear housing member 562, with a springproviding a clamping action 567 forcing the PCBs against one another.

According to FIG. 5, a user inserts a ballot 570 in an opening 580 abovethe PCBs 564 and 565 and between the pressing mechanism 561 and the rearhousing member 562. The opening 580 is positioned such that the loweredge of the ballot comes to rest in a seam between the two PCBs which,initially, are in contact with one another. The voter then pulls a lever(not shown), mechanically connected to the pressing mechanism 561, toseparate the PCBs 564 and 565 in opposition to the spring. The ballot570 falls downward between the PCBs 564 and 565, and comes to restagainst a stop 585. The lever is released and the ballot 570 is firmlyclamped by the PCBs 564 and 565. One skilled in the art will appreciatethat this approach is readily adapted to the ballot and HEA positioningschemes of FIGS. 4A and 4D.

After the ballot is received from the voter, the orientation sensors 563then inspect the ballot to confirm proper insertion and determine theorientation of the inserted ballot. The sensors detect the presence orabsence of orientation indicators on the inserted ballot. The relativepositions of the sensors match the relative positions of the locationson the ballot where orientation indicators may be present.

FIG. 6 shows a ballot labeling scheme and associated sensor positionsfor orienting a ballot according to the invention. In this scheme,orientation indicators are printed in several comers of the ballot.Specifically, orientation indicators 510 are printed in the lower left,upper left, and upper right corners of the front side of the ballot 500,and orientation indicators are printed in the lower right, upper left,and upper right corners of the back side of the ballot, as shown. Here,“front”, “back”, “upper”, and “lower” are defined relative to theprinted matter, e.g. a set of candidate's names and correspondingcheckboxes, on the ballot. Also shown in FIG. 6 are the four sensorpositions a, b, c, and d, corresponding to the four corners of theballot when in the inserted position. The indicators may be markings, asshown in FIG. 6 or may be holes punched through the ballot.

FIG. 7 shows four possible ballot orientations. Table 1 shows the sensorreadings a, b, c, and d corresponding to an improper ballot insertionand the four possible orientations of FIG. 7. Here, 1 corresponds to thedetection of an orientation indicator and 0 corresponds to no detectionof an indicator. The uniqueness of the rows indicates that each of thefour orientations can be uniquely determined given the pattern oforientation indicators and arrangement of sensors shown in FIG. 6. Itshould be noted that the scheme described above is also tolerant of asingle sensor failure—either “fail-on” or “fail-off”.

TABLE 1 Sensor readings and corresponding orientations. SensorOrientation a b c d No Ballot 0 0 0 0 Front Up 1 0 1 1 Back Up 0 1 1 1Back Down 1 1 1 0 Front Down 1 1 0 1

The ballot marking device may proceed with marking the ballot once theorientation of the ballot is determined. The manner in which the heatingelements are addressed, however, is adapted to reflect the determinedorientation of the ballot. For example, if the ballot marking deviceuses the ballot and HEA configuration of FIG. 4A-(2) and the insertedballot is a one-sided ballot formed of paper sufficiently insulative asto permit one-sided marking, only one of the two HEAs will be addressedto mark the ballot. Specifically, only the HEA facing the printed sideof the ballot is addressed during marking. If the inserted ballot is atwo-sided ballot formed of paper sufficiently insulative as to permitone-sided marking, both HEAs are addressed and the marking pattern withwhich each HEA is addressed is based on the side of the ballot facingthe HEA.

Additionally, the marking patterns with which the HEAs are addressed mayneed to be inverted vertically based upon the ballot orientation. Ifinstead the ballot marking device uses the ballot and HEA configurationof FIG. 4A-(1), the pattern with which the HEA is addressed is invertedeither horizontally, vertically, or horizontally and vertically based onthe ballot orientation. If all ballot orientations are to be acceptedusing the configuration of FIG. 4A-(1), however, the ballot must beformed of paper sufficiently conductive as to permit marking on bothsides of the paper from a single HEA on one side of the ballot. If moreinsulative paper is used, the voter may be instructed to insert theballot in one of the two acceptable orientations.

Other Applications

One skilled in the art will appreciate that aspects of the invention,while described herein with reference to a ballot marking device, mayfind use in other applications. In particular, the techniques formanufacturing two-sided thermal printing paper described in FIGS. 2 and3 may be useful in applications in which the thermally printable areacomprises a relatively small fraction of the entire paper area. Thepositioning schemes of FIG. 4 and the orientation scheme of FIGS. 6 and7 may find use in most any thermal printing application in which a userinserts single sheets of paper for printing.

As will be understood by those familiar with the art, the invention maybe embodied in other specific forms without departing from the spirit oressential characteristics thereof. Likewise, the particular naming anddivision of the members, features, attributes, and other aspects are notmandatory or significant, and the mechanisms that implement theinvention or its features may have different names, divisions and/orformats. Accordingly, the disclosure of the invention is intended to beillustrative, but not limiting, of the scope of the invention, which isset forth in the following Claims.

1. A thermal printing apparatus, comprising: a first plate having anarray of heating elements disposed thereon, individual heating elementswithin the array of heating elements separated from one another by aninsulating medium; at least one additional plate having at least oneadditional array of heating elements disposed thereon, individualheating elements within the at least one additional array of heatingelements being separated from one another by an additional insulatingmedium; wherein the first plate and the at least one additional plateare configured substantially adjacent to each other, with the array ofheating elements and the second array of heating elements facing oneanother, to form a slot between the first plate and the at least oneadditional plate, said slot adapted to accept a thermochromic printingmedium; and wherein the array of heating elements, the at least oneadditional array of heating elements, the insulating medium, and the atleast one additional insulating medium are configured such thatactuation of any one individual heating element marks the thermochromicmedium and is sufficiently insulated by the insulating medium or the atleast one additional insulating medium that it does not to bleed to anunintended region of the thermochromic medium.
 2. The thermal printingapparatus according to claim 1, wherein the first plate and the at leastone additional plate comprise printed circuit boards.
 3. The thermalprinting apparatus according to claim 1, individual heating elementsfrom the array of heating elements and the at least one additional arrayof heating elements comprising surface mount resistors.
 4. The thermalprinting apparatus according to claim 1, individual heating elementsfrom the array of heating elements and the at least one additional arrayof heating elements comprising shaped traces.
 5. The thermal printingapparatus according to claim 1, further comprising: a processor, coupledwith the first plate and the at least one additional plate, foractuating individual heating elements from the array of heating elementsand the at least one additional array of heating elements.
 6. Thethermal printing apparatus according to claim 5, further comprising: atleast one sensor coupled to a plate selected from among the first plateand the at least one additional plate, wherein the sensor is furthercoupled to the processor, wherein the sensor is configured to detect thepresence of at least one indicator on the thermochromic medium, andwherein the processor is configured to determine the orientation of thethermochromic medium based on the location of the at least oneindicator.